What is the field strength of a pulse in an air core coil?

AI Thread Summary
To calculate the magnetic field strength of a pulse in an air core coil, the user inquires about the field generated by a coil with 20 turns, a height of 20mm, and a pulse of 10V and 1A, with an inductance of 200uH. The approximate magnetic field (B) inside the coil can be estimated using the solenoid formula, yielding a value of 1.25 x 10^-3 Tesla or 12.5 Gauss. The user also seeks to understand how the coil's diameter, ranging from 150mm to 300mm, affects the field strength and how to calculate the B field at distances away from the coil. Additionally, they inquire about the impact of varying inductance values on the calculations. The discussion highlights the importance of using accurate measurements and formulas for precise calculations.
hj47
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I'm new to the forum, so hello!

How can i calculate the magnetic field strength of the pulse of an air core coil, the number of turns is 20 & the height of the coil is 20mm, not single or multi layered just random wound.
The pulse is 10V & 1Amp, the Inductance is 200uH.

Not sure how to go about this?
 
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There are several web-based inductance calculators, but they all give lower inductances than you measured. Once the inductance can be calculated approximately, the B field inside the coil can be estimated. You did not provide the coil diameter, which would be useful.
For now, the very approximate B field inside the coil using the solenoid formula is

B =u0 N I/z Tesla, where
u0 = 4 pi x 10-7 Henrys per meter
N = 20 turns
I = 1 amp
z = 0.02 meters

So B = 1.25 x 10-3 Tesla = 12.5 Gauss

One can also use the short coil formula from integrating the Biot-Savart Law yielding

B = (u0/2) N I/R (where R = radius)
= 1.25 x 10-3 Tesla = 12.5 Gauss using R = 1 cm (0.01 meters)
 
Thanks Bob S,

The coil Radius is 150mm--300mm Diameter, i am very interested to know how the diameter affects the field strength.

I see you mention the B field "inside" the coil, is there a way to calculate the strength of the B pulse at distance away from the coil, say 25mm 50mm 75mm etc?
Thanks Again, your post is very usefull!
 
Sorry Bob

Edited:

I am missing something,
u0 = 4 pi x 10-7 Henrys per meter, = Permeability of Air------Correct?


Say L Inductance is 300uH or 400uH instead of 200uH how does L fit into the equation?
 
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The integral of the Biot-Savart Law for a circular loop relates the current in a current loop of radius R carrying a currrent I to the magnetic field anywhere along the axis of the loop.

B = (u0/2) I R2/(x2+ R2)1.5
where units are meters, amps and Tesla. x is the distance along the axis from the center of the loop. uo is the permeability of free space.

Use the web calculator http://www.66pacific.com/calculators/coil_calc.aspx
to calculate inductance.
 
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